Field of the Invention
The present disclosure relates to a compressor motor, and more particularly to a compressor motor in which a plurality of magnets are inserted into a rotor.
Description of the Related Art
In general, a compressor that forms one element of a refrigerating cycle is provided with a compressor motor, and such a compressor motor is classified into several types in accordance with a driving method thereof. As an example, a capacity variable type compressor uses a brushless motor, and includes an inverter that is controlled by a controller. Such a variable type compressor generally uses a method for driving a compressor motor through applying of a voltage that is generated in accordance with a switching operation of a switching element provided in the inverter to motor windings.
Such a compressor motor is composed of a stator and a rotor, and the rotor is configured to electromagnetically interact with the stator and is rotated by a force that acts between a magnetic field and current that flows through a coil.
The rotor is briefly classified into a SPM (Surface Permanent Magnet) type in which magnets surround a rotor in accordance with the coupling structure thereof and an IPM (Interior Permanent Magnet) type in which magnets are buried and fixed into a rotor.
Since the SPM type rotor is surrounded by the magnets having uniform reluctance, there occurs no reluctance change, and thus the rotor is operated purely in dependence upon torques that are generated by the magnets. Accordingly, the torques generated per unit current become low to deteriorate efficiency of the rotor. Further, the SPM type rotor has the drawback that man-hour, such as a magnet bonding process, becomes complicated, and during high-speed rotation of the rotor, the magnet may secede from a core to form a gap between the magnet and the core. Further, eddy current may flow in a non-magnetic body to cause a power loss to occur.
Accordingly, the IPM type rotor, in which the magnets are buried and fixed into the rotor, has been proposed.
However, in an environment where the rotor is rotated at a low speed in order to heighten the efficiency of the motor, the magnets may be moved while the rotor is rotated at a constant speed, for example, at a low speed.
In the case where the magnets are moved as described above, the magnets may be deformed or damaged due to friction between the magnets and the core. Further, in the case where fine powder that is generated as the magnets are worn down is discharged together with a coolant that flows into a compression chamber of the compressor, a cylinder, a piston, and a valve device may be damaged. If the powder that is generated due to the abrasion of the magnets continuously circulates in the refrigerating cycle together with the coolant, an expansion valve may be clogged.
On the other hand, if the magnets, which are inserted into the rotor, have already been magnetized prior to the insertion, it is required to determine polarities of the magnets when the magnets are inserted into the rotor and to arrange the magnets so that the polarities of the magnets cross each other. Accordingly, it is required to confirm the polarities of the magnets one by one when inserting the magnets into the rotor, and this may cause a delay in a rotor manufacturing process.
In order to solve the delay problem in the rotor manufacturing process and to easily manufacture the rotor, non-magnetized magnets are inserted into the rotor. The magnets, which initially have no polarity, may have the polarities through a magnetization process in a state where the magnets are inserted into the rotor. Since the magnets have the polarities, the rotor may be rotated through electrical interaction with the stator on the inside of the stator. Through the rotation of the rotor, the driving force of the motor can be transferred to the compressor.
In this case, it is required to match the position of the rotor with a magnetization device so that a portion that becomes a magnetic pole of the non-magnetized magnet corresponds to the magnetic pole position of magnetic flux that is generated by the magnetization device. In the related art, in order to match the magnetization position of the rotor with the magnetization device, a guide hole is formed on an upper portion of the rotor, and a pin is inserted into the guide hole to match the rotor with the magnetization position. Further, during the magnetization, the rotor is fixed to the magnetization position by the pin.
However, in matching the magnetization position of the rotor using the guide hole and the pin and fixing the rotor to the magnetization position in the related art, the pin may not be accurately inserted into an insertion hole, and thus a cover may be broken to cause foreign substances to be generated. Further, during the magnetization, the pin may be damaged due to magnetization impacts. If the pin is damaged, the rotor is rotated by a rotating magnetic field that is formed in the magnetization process to cause the magnetization position to be distorted. Accordingly, the magnetization of the magnets may fail or may be insufficiently performed, and thus the performance of the motor that includes such a rotor may be deteriorated.